GNATS IRA-AOC Documentation

GNATS Production version 2.0 features IRA (In-Time Risk Assessment)

simulation. It has been built for look-ahead simulation to detect and report

potential accidents and flight failure.

Steps to run IRA:

1. Start GNATS Server on NAS Traffic Simulator.

2. Start GNATS Server on IRA Simulator.

3. Run GNATS_Client/sample/DEMO_TS.py on NAS Traffic Simulator.

4. On NAS Traffic Simulator, open GNATS_Client/sample/DEMO_TS.py, change

the TRX file name to the desired one for simulation and Run

GNATS_Client/sample/ DEMO_TS.py on NAS Traffic Simulator. Make sure the

TRX is present in the share/ directory of both, IRA and NAS Traffic Simulator.

4. Run GNATS_Client/sample/DEMO_IRA.py on IRA Simulator.

5. The results from IRA simulation will be sent to NTS and the output will be

displayed on the IRA GUI Agent.

The workflow of IRA is depicted by the following chart:

Region of Interest

Based on the use case, a select area of the airspace of ground can be set for

analyzing air traffic. This is called the region of interest. This reduces the

calculations required to determine safety and thereby makes simulation more time

efficient. Here are the functions that can be used to set and get region of interest:

int setRegionOfInterest(double[] regionBounds): This

function can be used to set the region of interest with the input parameter as a

double array of the latitude-longitude bounds of the region. The return data is a

flag indicating success or failure.

double[][] getRegionOfInterest(): This function can be used to get

the region of interest. The returned data is a nested double array of the latitude-

longitude bounds of the region.

Region of Regard

For each aircraft, based on the flight phase it is in, there is a region within which

other aircraft or objects pose a potential risk. This is called the region of regard.

GNATS has preset regions of regard for aircraft based on the flight phase, and it is

as follows:

However, the user has the ability to change these bounds based on the situation

requirements. These functions have been built into GNATS to provide this feature:

int setRegionOfRegard(String aircraft, String

flightPhase, double[] regionBounds): This function can be used to

set the region of regard with the input parameter as a double array of the latitude-

longitude bounds of the region. The return data is a flag indicating success or

failure.

double[][] getRegionOfRegard(String aircraft, String

flightPhase): This function can be used to get the region of regard. The

returned data is a nested double array of the latitude-longitude bounds of the

region.

To get flights that are contained within the preset or user defined region of regard,

following function can be used:

String[] getAircraftInRegionOfRegard(String aircraft):

This function returns a string array of the callsigns of all the aircraft within the

region of regard for the aircraft provided as the input parameter.

Accident Occurence Categories (AOC)

GNATS has equipped with 13 AOC categories that all denote the potential risks

that aircraft, ground vehicles might face during operations and flight. They are as

follows:

Ground Collision (GCOL): A collision between aircraft or ground vehicles during

taxi phase.

Taxiway Excursion (TE): Lateral or longitudinal excursion of an aircraft or ground

vehicle during taxi phase.

Taxiway Incursion (TI): Lateral incursion of aircraft or ground vehicle during taxi

or Longitudinal incursion of an aircraft while landing.

Runway Excursion (RE): Lateral excursion of aircraft or ground vehicle during

takeoff/drive.

Runway Incursion (RI): Collision between aircraft taking off and an

aircraft/ground vehicle crossing the runway.

Wake Turbulence (WAKE): A trailing smaller aircraft flying into the wake vortex

caused by a leading heavier aircraft.

Collision with Obstacles during Takeoff (CTOL): Aircraft not being able to clear

an obstacle (Airport compound wall or building up to 35 ft) during take off.

Runway Undershoot (US): Aircraft landing before the start of the runway due to

steeper than needed glide slope.

Runway Overshoot (OS): Aircraft not able to stop after landing or take off before

runway ends.

Mid Air Collision (MAC): Two aircraft colliding mid air.

Misaligned Landing (ML): When the aircraft landing is not aligned per runway

center line and is drifting away.

Controlled Flight into or towards terrain (CFIT): An aircraft’s line of sight is

headed towards collision into terrain.

Wind shear or thunderstorm (WSTRW): An aircraft approaching a convective

weather event.

The general algorithmic principle of calculating proximity and approach of

vehicles towards each other to detect and analyze risk is as follows:

IRA and NAS Traffic Simulator (NTS) are together used to have this look ahead

simulation that runs for the aircraft within the region of interest and based on the

individual aircraft’s region of regard. The AOCs are reported using the IRA GUI

Client as follows:

CFIT

CTOL

GCOL

MAC

WAKE

WSTRW